Safety device for boilers



Jan. 1, 1929. H I 1,697,621

c. A. TWIGG ET AL SAFETY DEVICE FOR BOILERS Filed July 2. i920 u I I III Patented Jan. 1, 19 29.

UNITED CHARLES A. TWIGG .AND

TES

ANDREW G. SPINNEY, OF PORTLAND, MAINE.

SAFETY DEVICE FOR BOILERS.

Application filed. July 2,

This invention relates to improvements in safety devices for boilers.More especially it relates .to devices particularly adapted for domestichot water service boilers and provides relief for such from excess oftemperature or pressure or a combination of both.

It is common practice today to connect hot Water boilers direct to themunicipal supply and thereby subject them constantly to the staticpressure of the main. Occasionally much higher pressures may be imposedupon the boiler, for example, the pressure due to water hammer. Faucetswhich can be turned from full on to full off in a half rotation of theirhandles cause such sudden stoppage of flow that severe water hammersoccur and, because of the well nigh incompressibility of Water. exertdangerous pressures on the boil er. These suddenly applied pressures mayand usually do take place at ordinary boiler temperature and thereforeto protect the boiler the invention provides relief from excessivepressure alone.

Under different conditions Where there may be an opening in the systemsufliciently large to prevent formation of any excess pressure, or wherefor some unaccountable reason the supply may be temporarily out oif, avery high temperature may be developed which would'melt the solderedjoints and cause the boiler to leak. The invention also provides twomeans of relief from such high temperature conditions.

But this invention goes further than simply giving relief from eitherpressure or temperature alone and provides other means which respond toeither excessive temperature or pressure alone, or to a. combinationthereof and insure, the safety of the boiler in case any or all of theother relief elements fail. And it is also a feature of this lastmentioned means that still another safeguard is pro vided which in timeefi'ectsa condition which necessitates a resetting of the device andthereby insures its inspection and care. This is important since theaverage house owner assumes that any safety device is in workingcondition and seldom, if ever, takes the trouble to test or inspect thesame with the result that after a while the device may becomeinoperative and afford no protection at all. Each time a deviceembodying the present invention operates either in response to pressurealone, temperature alone or what is usual to both, a slight change inthe relation of cer- 1920. Serial No. 393,590.

tain parts is effected which ultimately produces a condition thatindicates the need of inspection and probable replacement of some of theparts. The appended drawings disclose one mode in which the principlesof the present inven-' tion may be applied. A safety valve is providedat the top of the boiler and arranged to open outward. Normally thisvalve is maintained seated by an externally applied closing pressurewhich can be adjustedto be overcome at any desired pressure. Below thevalve, and extending wellinto the boiler, is a thermoresponsive membersuitably anchored and having its highly expansible element arranged toexert pressure outward on the valve to overcome the aforementionedclosmg pressure. and thereby open the valve. In case, however, thenormal closing pressure is augmented by otherconditions, such as anadditional weight aiding it. orconr'osion causmg the moving parts tostick, the invention provides further relief by arranging-for the strutwhich transmits the closing pressure to bottom upon a soft metal blockin the top of the valve. In consequence under abnormal conditions wherethe strut could not be moved either by high pressure of the contentsacting on the valve, or by pressure imposed by the expandingthermo-responsive element, the soft metal block will yield to permitrelative movement between the strut and the valve an d thereby unseatthe latter. In fact each time the valve is raised, the natural inertiaof the movingparts causesthe sharp point of the strut to be forced intothe soft metal block asmall amount so that as the valve reseats, thestrut and other moving parts applying the closing pressure are slightlynearer the valve seat. A fixed stop in the path of one of these partsfinally limits the degree of ap- ,In its preferredform disclosed hereimade- I vice embodying'the principles of theinvention may be constructedas a fitting to go on; the ordinary out-let of a boiler havlng itself asuitable outlet for connection with the distributing pipe of the housesystem and another outlet leading to a drain or waste pipe. A singlevalve servesto out off this latter outlet but leaves a free open passagefrom the boiler opening to the distributing outlet. And by a uniquearrangement of parts, the several elements which are operative( inconnection with the different reliefs provided,

are organized to exert their respective influence upon the single valve.

It is intended that the patent shall cover through the body of thedevice with certai of the parts in full View; and

Figure 3 is'a; plan of a section, on line of Figure 1, through thedevice.

Referring particularly to the drawings 1 there is attached to the upperportion of a hot -with two holes leading to impose a predetermined forceupon the.

water boiler 1,-about the outlet 2, a relief device 3 having a chambertherein with outlet 4 adapted to be connected to the-distributing pipeofthe house system. At substantially the level of the upper side-of thisoutlet, the casing of the device is belled outward to form a sphericalseat for a valve 5 whose lower face is also of spherical sha to fit thisseat. A series of holes are provided in the valve near its edge in whichare embedded fusible plugs 6. On its underside the valve hasguidememhers 7 for positioning the valve properly on. his seatand' onits upper side has a hollow hub from the hollow through the valve. Theseholes and thehollow of the hub are'likewise filled with soft metalpreferably fusible, the latter constituting what will hereinafter betermed the block 8.

- Above the valve, the chamber has a side outlet 9 for connection with adrain, and a top cover having a hole therethrough to accommodate a strut10. The latter has asharp pointed .end that rests on the soft metalblock 8. This strut extends through the cover and cont-acts with a lever11, pivoted at 12 on the cover. Beyond its contact'with the strut 10,the lever has a weight 13 adjustable along it strut and through it uponthe valve to hold the latter upon. its" seat. Preferably an elongatedbushing 14 is prbvided in the cover both to prevent leakage around thestrut 10, and to aid in positioning the strut so that its sharp pointwill rest on the block 8. There is also on the cover 'a'stop 15 in thepath of swing of the lever 11 and adapted, as-will more particularlyhereinafter appear, to cut off theforce of the weight 13 from thestrut10 and thereby prevent the valve from being held .to its seat by theexternally applied force.

Below the valve is arranged a thermo-responsive element or rod 16 whichextends for a considerable distance downward into the hot water. Itsfree or movable end is seated in a slight depression or recess in thebottoma face of the valve at its center while its other or anchored endis supported by a plate 17 fastened to the lower ends of two rods 18which at their upper ends are secured to the change in temperature) theforce exerted internally on the valve 5 should lift it from its seatwhen said internal force overcomes the closing pressure applied to thevalve through the strut'lO. Thus one form of relief is provided by thedevice for excessive pressure alone. In case, however, someone has putadditional weight on the lever-11, as by hanging purpose ofmore tightlyseating the valve (and thereby stopping what might have been a very slowleak) ,.or if the bushing 14 binds too tightly on the strut 10 orcorrosion has occurred there or at the pivot 12 all or any of whichwould prevent the strut from being pushed upward by the excessivepressure within the boiler, the device nevertheless providesrelief'because the pressure exerted from within can ush the valvebodilyagainst the strut 10. so doing the sharp. point of the strut penetratesthe soft metal block 8. Thus another form of relief is provided forexcess sive pressure alone.

- IVhen there is no increase of pressureof any moment but thetemperature is raised too high .for safety the expansible rod 16pressing on the valve. can lift the strut and weighted lever and thusvent the system before any damaging pressure is generated,

either by expansion of the water or byits conversion into steam. Asbefore noted, if the strut cannot be moved the expanding rod 16 canforce the valve and block upward about the strut and thus unseat thevalve. In fact, it is ust such a condition of increase of temperaturethat enables the function of the soft block 8 to be best utilizedbecause the high temperature which causes the rod 16 to expand alsoserves to further soften the fusible block 8, making it even nioresusceptible to penetration by the sharp point of the strut.

And finally, if the strut cannot be moved,

some foreign article on the lever for the or'the anchor plate 17 hasbecome loose from its supports, or the valve sticks to its own seat,any'or all of which conditions might occur after a considerable lapse oftime, the fusible block 8 could melt and run through the branches in thevalve, and the separate plugs 6 could fuse and thus open up severaloutlets through the valve for relief of the boiler. v

While the different kinds of reliefs have been described separately forthe purpose of making the several possible actions clear, it

should be borne in mind thatthe operation of the different parts is byno means a series of separate happenings. Whenever the valve and block 8are raised, whether by pressure or temperature acting .alone, there willbe a slight penetration of the block by the pointed end of the strut. Ofcourse most of the movements of the valve are due to a combined changein pressure and temperature conditions and conseqently almost every timethe block is lifted it is at that time relatively soft and more easilypenetrated by the strut. Each time this occurs and the boiler has beenrelieved the valve will again tend to seat under the action of t 1eweight 13. The bearing point, however,between the block and strut willbe lower than initially owing to the penetration of the block by thestrut and consequentl the strut will move to a lower position be orebrought to rest and th lever 11 will be nearer to the stop 15. .A terthe device has operated a number of times the cumulated penetration .ofthe block by the strut will bring the lever to rest on the stop 15. Whenthis occurs the valve'of course will not be tight on its seat as will beevidenced by a leaking of the valve or by its chattering. Eithercondition indicates need of attention and insures that the valve must bere-fitted with another block and put again into operable condition. Thisnecessity of keeping the device in workable condition is a factor in itsfavor, because when once installed in a household it would ordinarilyreceive little attention and would be allowed to reach a condition whereit would not provide the greatest safety for the boiler.

'lVe claim:

1. A safety device for hot water boilers and the like comprising, incombination, a valve casing having an inlet adapted for connection withan outlet from the boiler; a discharge outlet from said casing in opencommunication with said inlet for service discharge of the boiler; arelief outlet from said casing; a pressure relief valve interposedbetween said relief outlet and said inlet having a penet-rable bearingon its external face; means holding said valve closed against normalwater pressure and adapted to yield under excess pressure, having amember resting against said bearing and adapted topenetrate therein uponmovement of the valve in valve casing having an inlet at one end adaptedfor connection with the boiler; a discharge outlet in the side of saidcasing in open communication with the inlet for service discharge of theboiler; a relief outlet in the side of said casing beyond said dischargeoutlet; a valve seat arranged across said casing between said out-lets;a valve on said seat shutting off said relief outlet from normaldischarge having a hollow hub with penetrablc metal therein; meanscomprising a member resting against said penetrable metal for holdingsaid valve closed against boiler pressure and adapted to yield when saidpressure exceeds a predetermined degree{ and thermostatic means affectedby rise of temperature of said water for forcing-said valve against thesaid member of said holding means and thereby effect the opening of saidvalve.

3. A safety device for boilers and the like, comprising, in combination,a valve casing having an inlet adapted for attachment to an outlet fromthe boiler; a discharge outlet from said casing in' open communicationwith said inlet; a relief outlet in said casing;'a

pressure relief valve cutting off said relief outlet from said inlethaving a recess in its lnner face; means holdlng said valve closed andadapted to yield under excess pressure in the boiler; and thermostaticmeans responsive to temperature rise in said boiler, comprising a yokeextending through said inlet and boiler outlet into the boiler and anexpansible bar having one end attached to said yoke and the other endresting in said recess of said valve and adapted upon expanding to liftsaid valve from its seat.

4. A safety device for a boiler comprising,

in combination, a relief valve having a penetrable bearing on itsexternal face; means applying external pressure to said valve comprisinga member resting against said bearing and adaptedto penetrate thereinupon the valve being opened; and a stop arranged to resist the pressureimposed by said means when said penetration has reached a predeterminedlimit consequent upon'successive openings of the valve.

5. A safety devicefor a boiler comprismg, in combination, a relief valvehaving a hollow hub on its external face and holes leading therefrom tothe internal face of the valve; a block of fusible metal in said hollowand said holes; meansapplying external pressure to seat said valvecomprising a pointed member resting against said block; thermostaticmeans responsive to temperature change in said boiler arranged to applan opening pressure on said valve to lift 1t rom its seat and effect aslight penetration ofsaid after a series of openings of said valve, saidmember in said block, whereby upon re-seat' closing pressure is withheldfrom the valve.

ing of the valve the means applying the ex- In testimony whereof We haveaffixed our 10 ternal pressure are nearer to the said-valve; signatures.I} and a stop interposed in the path of the last mentioned meanslimiting the extent to which r CHARLES A. TWIGG. said means can approachthe valve vhereby, ANDREW G. SPINNEY

